An arrest warrant was issued on Tuesday for a key suspect in the murder of Wannee Jiracharoenying, 58, whose decomposing body was found in a refrigerator at a house in Chiang Mai's Chom Thong district on Sunday.

The suspect was identified as 39-year-old Withun Sitabut from Lampang, who is now wanted by police on charges of robbery resulting in the death of Wannee, a millionaire from Samut Prakan.

Wannee was reported missing by her brother, Worapan, on Sunday after friends and family were unable to contact her for two weeks. She usually stayed at the house in Chom Thong district while practising dharma.

Police investigators have reportedly obtained evidence and eyewitness accounts that Mr Withun, also a driver of a yellow songthaew passenger truck on the Chom Thong-Chiang Mai route, had lied to a relative of Wannee, and sent a text message from Wannee's phone saying that she was travelling to Vietnam. 

Police said he was also filmed on a security camera using Wannee's ATM card to withdraw money in Rayong, before abandoning Wannee's BMW, which he had stolen from her, and leaving on the back of a motorcycle taxi. Mr Withun was also reportedly caught on camera withdrawing cash from ATMs in Chiang Mai, Lamphun and Lampang before heading to Rayong. 

Mr Withun, who lives with his wife and two children in Chom Thong district, first met Wannee when he picked up a group of Buddhist nuns, including Wannee, and drove them to Wat Phrathat Si Chom Thong. 

Mr Withun and Wannee allegedly then became good friends and he was sometimes seen holding shopping bags for her at their local mall. 

According to police, after murdering Wannee, Mr Withun drove Wannee's car to pick up his wife and children to go on a trip to neighbouring Chiang Rai, and later took them back to their home. Following the murder, he reportedly spent a lot of money, some of which he transferred to his wife so that she could buy gold ornaments.